The present invention relates to a wiring circuit board in which an electronic device (e.g., chip capacitor, chip inductor, and chip resistor) is embedded in its insulating substrate using an embedding resin for that. This type of wiring circuit board is suitable for multilayer wiring circuit boards and semiconductor-device-received packages.
In recent years, there have been studies of mutichip modules (MCM) in which many semiconductor devices are mounted on a buildup wiring circuit board. For mounting electronic devices (e.g., chip capacitor, chip inductor, and chip resistor), it is general to conduct a surface mounting in which the electronic devices are mounted on a wiring layer (formed on the surface of a substrate) by using a solder.
However, when such electronic devices are mounted on the surface of a buildup wiring circuit board, it is necessary to have a certain area for mounting each electronic device. Therefore, this becomes an obstacle in the way of producing smaller wiring circuit boards. Furthermore, the wiring arrangement upon the surface mounting may increase undesirable parasitic inductance. Therefore, to follow higher-frequency electronic apparatuses becomes difficult.
In order to solve the above-mentioned problems, there have been studies of embedding electronic devices in the inside of an insulating substrate.
Japanese Patent Unexamined Publication JP-A-11-126978 discloses a method for putting an electronic device in a hole of an insulating substrate. In this method, a laminate is prepared by forming a wiring circuit layer on a transfer film and then by mounting the electronic device on the wiring circuit layer. The resulting laminate is placed on the insulating substrate in a manner to put the electronic device into the hole. In this method, however, a precise positioning of the electronic device may be difficult. JP-A-2000-124352 discloses a multilayer wiring circuit board in which an insulating layer is formed on an electronic device embedded in a core substrate. JP-A-9-46046 discloses another multilayer wiring circuit board having an electronic device embedded therein.
In case that an electronic device is embedded in the inside of a core substrate, it is necessary to put the electronic device in a void space of the core substrate, then to fill the void space with a resin, and then to connect an electrode of the electronic device with a wiring by electroless plating or the like. In this case, it may be difficult to have a sufficient adhesion between the resin surface and a plating layer (wiring layer). This may cause a blister of the plating layer in a reliability test.
It is therefore an object of the present invention to provide a wiring circuit board that is capable of providing a superior adhesion of a wiring layer to a resin used for embedding an electronic device in the wiring circuit board.
It is another object of the present invention to provide a wiring circuit board that is substantially free from a blister of the wiring layer and has high reliabilities in reliability tests (e.g., heat shock resistance test and water resistance test).
According to the present invention, there is provided a wiring circuit board comprising:
an electronic device disposed in a hole of said wiring circuit board;
a resin filling said hole such that said electronic device is embedded in said resin;
a wiring layer formed on said resin; and
an interface between said resin and said wiring layer, said interface having a roughness in a range of 2-6 xcexcm in terms of ten-point mean roughness.
According to the present invention, there is provided a method for producing the wiring circuit board. This method comprises the steps of:
(a) forming said hole in a core substrate of said wiring circuit board;
(b) disposing said electronic device in said hole;
(c) filling said hole with a resin, thereby embedding said electronic device in said resin;
(d) making a surface of said resin rough; and
(e) forming said wiring layer on said surface of said resin.